1) Field of the Invention
The present invention relates to an organic coloring matter, a composition comprising the organic coloring matter and a photo-recording medium comprising the organic coloring matter.
More particularly, the present invention relates to an organic coloring matter having an excellent resistance to ultraviolet rays, and a satisfactory resistance to near infrared rays and heat, a composition containing the organic coloring matter, and a photo-recording medium containing the organic coloring matter.
2) Description of the Related Arts
Recently, many inventions have been proposed for photo-recording media containing organic coloring matter enabling a recording and erasing of the record, which are nonpoisonous and cheap, in comparison with conventional inorganic photo-recording media.
These photo-recording media are classified into three groups.
The first group consists of photo-recording media composed of a substrate and a coating layer formed on the substrate, and comprising a coloring matter sublimated or melted by irradiating a recording a laser beam thereto in accordance with digital signals, to form pits corresponding to those signals in the coating layer.
The information recorded in the coating layer can be read by irradiating a reading laser beam to the coating layer, and detecting differences in the reflectance of the laser beam between the pitted portions and non-pitted portion of the coating layer.
The second group consists of photo-recording media composed of a substrate and a coating layer formed on the substrate, and comprising a mixture of a coloring matter and a resinous material. When a recording laser beam is irradiated to this coating layer, the resinous material is melted or decomposed to form recording pits in the coating layer.
The third group consists of erasable photorecording media composed of a substrate, and a coating layer formed on the substrate and comprising a coloring matter and a resinous material. By irradiating a recording laser beam in accordance with digital signals corresponding to the information to be recorded, pits or bumps are formed to contain the information in the recording layer, and that information can be read by irradiating a reading laser beam. Also, the recorded information can be erased by irradiating an erasing laser beam on the recorded coating layer, and erasing the pits or bumps.
In the above-mentioned photo-recording media, the coloring matter has the following functions.
In the recording step, the coloring matter absorbs the recording laser beam and converts the absorbed energy of the laser beam to heat. This heat serves to form pits or bumps in the recording layer.
Also, in the reading step, the coloring matter in the coating layer reflects the reading laser beam applied to the coating layer.
Further, depending on the type of recording media, the phase or chemical constitution of the coloring matter per se is changed in the recording step.
Accordingly, the coloring matter to be contained in the photorecording media must have an absorption band and a reflection band in the oscillator wavelength ranges of the recording laser beam and the erasing laser beam. Also, the coloring matter must have a high chemical stability so that, in a re-recording type media, the coloring matter exhibits a high durability to repeated reading operations, and in an erasable type media, the coloring matter exhibits a high durability to repeated recording and erasing operations.
Typical near infrared ray-absorbing coloring matters having a high durability and exclusively usable for recording-erasing type media are naphthalocyanine compound coloring matters as disclosed in Japanese Unexamined Patent Publication Nos. 61-177,287, 61-177,288, 64-11,982, 63-227,387, 64-4,389, 64-77,582, 1-145,195 and 2-663, phthalocyanine compound coloring matters as disclosed in Japanese Unexamined Patent Publication Nos. 1-130,984, 1-138,905 and 1-130,980, and stabilized cyanine dye complex coloring matters in which a cyanine dye compound cation is stabilized by a paired specific transition metal complex anion, as disclosed in Japanese Unexamined Patent Publication Nos. 60-103,532, 61-8,384, 61-11,294, 61-16,891, 62-14,345, 2-3,374 and 2-4,580.
Generally, the conventional naphthalocyanine and phthalocyanine compounds exhibit a very poor solubility in an organic solvent, and thus a plurality of synthesizing steps are necessary to convert these compounds to organic solvent-soluble compounds.
Also, although the conventional stabilized cyanine dye complex coloring matters exhibit an enhanced resistance to near infrared rays and to heat, in comparison with the non-stabilized cyanine dye compounds, they are disadvantageous in that they have a poor resistance to ultraviolet rays, and thus are easily deteriorated to the same extent as the conventional non-stabilized cyanine dye compound.
Accordingly, when a recording layer is provided by using a composition comprising the conventional stabilized cyanine dye complex coloring matter and a resinous material capable of being cross-linked by an ultraviolet ray irradiation, the resultant photorecording media is disadvantageous in that the recording property of the coating layer is deteriorated when the resinous material is cured by the irradiation of ultraviolet rays.
Also, it is impossible to avoid the deterioration of the conventional coloring matter in the coating layer when ultraviolet rays are applied to cure a bonding resin layer, protective resin layer or sealing resin layer of the photorecording media.